1. Field of the Invention
The present invention relates to a clean box constructed in such structure that objects to be transferred, necessary for fabrication processes of semiconductors, electron-device-associated products, optical disks, etc., can be transferred in a sealed state with a clean gas containing no contaminants and, particularly, in such structure that the objects to be transferred are carried through a side aperture into or out of the box, and also relates to a clean transfer method and apparatus using this clean box.
2. Related Background Art
Transfer boxes using the mechanical seal as illustrated in FIG. 6 have been used heretofore for transferring semiconductor wafers or the like.
The assignee of the present invention suggested a clean transfer method for transferring the objects to be transferred, in a vacuum clean box in a vacuum-sealed state in Japanese Laid-open Patent Application No. 7-235580. In this case, the vacuum clean box is composed of a box body having an aperture in a bottom surface and a bottom lid also serving as a shutter for hermetic sealing, and a closed state thereof is maintained in such a way that the bottom lid is urged against the box body by a pressure difference between inside and outside the box (the inside of the box being a vacuum and the outside the atmospheric pressure). In cases where the transfer is carried out while the inside of the clean box is filled with a clean gas such as nitrogen or the like, the above structure cannot maintain the closed state of the bottom lid without any aid, because there is no pressure difference between inside and outside the box.
The assignee of the present invention thus suggested in Japanese Laid-open Patent Application No. 10-56050 a clean box that permitted the objects to be transferred in the sealed state with the clean gas, without use of the mechanical seal.
The clean box of the clean gas sealing type suggested in Japanese Laid-open Patent Application No. 10-56050 is illustrated in FIG. 5. In this figure, the clean box 1 has a box body 2 having an aperture in the bottom surface, a bottom lid 3 for hermetically closing the aperture of the bottom surface and also serving as a shutter, and a lid chuck 4 of an L-shaped cross section and an annular shape for adhering under vacuum to the box body 2 and lid 3 and maintaining the lid 3 in the closed state, but has neither evacuation means nor transfer means. A holder 5 is attached to the bottom lid 3 and supports the objects 6 to be transferred, for example, in a multiply stacked state in the clean box 1.
In this case of FIG. 5, an inside space K of the lid chuck 4 is kept in a vacuum-evacuated state, whereby the lid chuck 4 maintains the bottom lid 3 in a pressed state against the box body 2 by the pressure difference between inside and outside. This structure allows the bottom lid 3 to be maintained in the closed state even if the inside of the clean box 1 is filled with the clean gas of the atmospheric pressure.
Incidentally, the clean box 1 of FIG. 5 is of the bottom opening/closing type, in which vertical motion as indicated by an arrow A is essential to the operation of carrying the objects 6 into or out of the box. This involves change in the height of the objects 6 from the floor surface, so that the excess vertical motion is required, in addition to the horizontal motion for interface with various processing devices. In addition, a vacuum changer having an evacuation function is used for attachment/detachment of the bottom lid 3 and lid chuck 4 to or from the box body 2 and for a process for depressurizing the inside space K of the lid chuck 4 into a vacuum in connection with the attachment, and vertical motion thereof is necessary for carrying the objects 6 into or out of the box. This poses a problem that the placement height of the clean box 1 on the vacuum changer also becomes high.
Further, the vacuum changer needed to have mechanisms capable of moving the bottom lid 3 and the lid chuck 4 up and down independently of each other, so that the structure of the vacuum changer tended to become complicated.
Meanwhile, standardization of the transfer boxes for semiconductors is under way in EIAJ (J300). The transfer boxes heretofore were of the type of taking the semiconductor wafers out of the bottom side of the box, but a laterally drawing method is being determined as a standardized method for the reason that the placement height of the box is high in the bottom opening/closing type. For example, the transfer box 20 for semiconductors of FIG. 6 suggested at present is also of the side open type having an aperture 21 in a side surface. This box, however, still leaves us the following challenges because of the mechanical seal; (1) a complex mechanism is necessary and sufficient reliability cannot be assured; (2) holding power sufficient for practical use cannot be obtained because of utilization of the mechanical holding power of springs or the like.
A first object of the present invention is, in view of the above points, to provide a clean box that does not have to use the conventional mechanical seal with the springs or the like even in the structure of the side open type, that can transfer or store the objects to be transferred in a sealed state with a clean gas, and that has simple structure.
A second object of the present invention is to provide a clean transfer method and apparatus capable of transferring the objects to be transferred in the sealed state with the clean gas, using the clean box of the side open type in the simple structure without use of the mechanical seal.
The other objects and novel features of the present invention will become apparent in the description of the embodiment hereinafter.
For accomplishing the above objects, a clean box of the present invention comprises a box body, said box body having an aperture in one side surface, an annular groove for suction formed in said one side surface so as to surround the aperture, and an intake/exhaust port in communication with said annular groove for suction in another surface; a side lid arranged to hermetically cover said annular groove for suction to form a space for suction while being mounted on the box body, said side lid being sucked to the box body by a pressure difference between inside and outside the space for suction to hermetically close said aperture; and an additional lid for hermetically closing said intake/exhaust port by a pressure difference between inside and outside thereof, the clean box itself having neither evacuation means nor transfer means.
A clean transfer method of the present invention is a clean transfer method using a clean box comprising a box body, said box body having an aperture in one side surface, an annular groove for suction formed in said one side surface so as to surround the aperture, and an intake/exhaust port in communication with said annular groove for suction in another surface; a side lid arranged to hermetically cover said annular groove for suction to form a space for suction while being mounted on the box body, said side lid being sucked to the box body by a pressure difference between inside and outside the space for suction to hermetically close said aperture; and an additional lid for hermetically closing said intake/exhaust port by a pressure difference between inside and outside thereof,
said clean transfer method comprising steps of hermetically connecting said clean box to a gate aperture of a clean device, the gate aperture being formed in a side wall surface of the clean device and being hermetically closed by a gate valve; evacuating a hermetically closed space outside the box body, including said additional lid, by a vacuum changer to cancel the pressure difference between inside and outside of said additional lid and opening said intake/exhaust port to turn said space for suction into the atmospheric pressure through said intake/exhaust port; thereafter drawing the side lid into said clean device while holding said side lid by said gate valve to establish communication between an inside space of said clean box and the inside of said clean device; and transferring objects to be transferred between said clean box and said clean device.
The clean transfer method can be arranged in such a manner that from the communication state between the inside space of said clean box and the inside of said clean device said side lid is held by said gate valve so as to hermetically close said aperture, thereafter said space for suction is evacuated through said intake/exhaust port by said vacuum changer, thereafter said intake/exhaust port is hermetically closed by said additional lid, and the hermetically closed space outside the box body, including said additional lid, is turned into the atmospheric pressure, whereby the side lid and additional lid can be mounted on the box body.
Further, a clean transfer apparatus of the present invention is a clean transfer apparatus comprising:
a clean box comprising a box body, said box body having an aperture in one side surface, an annular groove for suction formed in said one side surface so as to surround the aperture, and an intake/exhaust port in communication with said annular groove for suction in another surface; a side lid arranged to hermetically cover said annular groove for suction to form a space for suction while being mounted on the box body, said side lid being sucked to the box body by a pressure difference between inside and outside the space for suction to hermetically close said aperture; and an additional lid for hermetically closing said intake/exhaust port by a pressure difference between inside and outside thereof;
a clean device having a gate aperture formed in a side wall surface thereof and a gate valve capable of opening or closing said gate aperture and capable of holding the side lid of the clean box connected to the gate aperture; and
a vacuum changer for evacuating a hermetically closed space outside the box body, including the additional lid of the clean box connected to said gate aperture,
wherein in a state in which said vacuum changer cancels the pressure difference between inside and outside of said additional lid and opens said intake/exhaust port to turn said space for suction into the atmospheric pressure through said intake/exhaust port, said side lid is drawn into said clean device while being held by said gate valve, to establish communication between an inside space of said clean box and the inside of said clean device.
The clean transfer apparatus may also be so constructed that said vacuum changer has a box holding member constructed in such structure that a vacuum suction passage for suction of said box body is formed in an opposite surface thereof to said box body and that said hermetically closed space is formed inside said box holding member.
Further, the clean transfer apparatus may also be so constructed that said vacuum changer has a lid receiver for receiving said additional lid separated from said box body, inside said box holding member, said lid receiver being movable.
The clean box according to the present invention has neither the evacuation means, e.g., a vacuum pump for evacuating the inside of the box or only the lid portions (the side lid and additional lid) of the box and other valves, pipes, etc. forming an evacuation system, nor the transfer means for transferring the box itself.